title: Self-organization of bacterial biofilms is facilitated by extracellular DNA.
abstract: Twitching motility-mediated biofilm expansion is a complex, multicellular behavior that enables the active colonization of surfaces by many species of bacteria. In this study we have explored the emergence of intricate network patterns of interconnected trails that form in actively expanding biofilms of Pseudomonas aeruginosa. We have used high-resolution, phase-contrast time-lapse microscopy and developed sophisticated computer vision algorithms to track and analyze individual cell movements during expansion of P. aeruginosa biofilms. We have also used atomic force microscopy to examine the topography of the substrate underneath the expanding biofilm. Our analyses reveal that at the leading edge of the biofilm, highly coherent groups of bacteria migrate across the surface of the semisolid media and in doing so create furrows along which following cells preferentially migrate. This leads to the emergence of a network of trails that guide mass transit toward the leading edges of the biofilm. We have also determined that extracellular DNA (eDNA) facilitates efficient traffic flow throughout the furrow network by maintaining coherent cell alignments, thereby avoiding traffic jams and ensuring an efficient supply of cells to the migrating front. Our analyses reveal that eDNA also coordinates the movements of cells in the leading edge vanguard rafts and is required for the assembly of cells into the "bulldozer" aggregates that forge the interconnecting furrows. Our observations have revealed that large-scale self-organization of cells in actively expanding biofilms of P. aeruginosa occurs through construction of an intricate network of furrows that is facilitated by eDNA.
authors.affiliation: The ithree institute, University of Technology Sydney, Ultimo, NSW 2007, Australia.
authors.forename: Erin S
authors.initials: ES
authors.lastname: Gloag
authors.forename: Lynne
authors.initials: L
authors.lastname: Turnbull
authors.forename: Alan
authors.initials: A
authors.lastname: Huang
authors.forename: Pascal
authors.initials: P
authors.lastname: Vallotton
authors.forename: Huabin
authors.initials: H
authors.lastname: Wang
authors.forename: Laura M
authors.initials: LM
authors.lastname: Nolan
authors.forename: Lisa
authors.initials: L
authors.lastname: Mililli
authors.forename: Cameron
authors.initials: C
authors.lastname: Hunt
authors.forename: Jing
authors.initials: J
authors.lastname: Lu
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Osvath
authors.forename: Leigh G
authors.initials: LG
authors.lastname: Monahan
authors.forename: Rosalia
authors.initials: R
authors.lastname: Cavaliere
authors.forename: Ian G
authors.initials: IG
authors.lastname: Charles
authors.forename: Matt P
authors.initials: MP
authors.lastname: Wand
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Gee
authors.forename: Ranganathan
authors.initials: R
authors.lastname: Prabhakar
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Whitchurch
mesh_terms: D018441:Biofilms; D004269:DNA, Bacterial / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial
keywords: collective behavior; swarming; t4p; tfp; type IV pili